RUNNING IDLE

I have 2 Vanagons 90 and 83, my 83 Westphalia Vanagon was running fine, then the idle started 'running'. On cold start it would idle fine as the auto choke warmed up, then after about a minute the idle would drop to normal and start to run or jump up and down. This van has 2 idle control switches mounted to the throttle body, I replaced the lower one which has a roller at the end of its switch. Still runs up and down. The other part # 411 927 211 is NLA from VW. So I replaced the Idle Stabilizer Control Box or DLS box part # 361 906 083, but it still jumps. Any ideas?
thanks for any input!

AIR FLOW METER
All engine air is drawn through the air flow meter. The meter contains a tunnel with measuring flap and dampening flap (offset 90 on same casting). The measuring flap swings in air stream against pressure of a spiral spring and is connected to a potentiometer.
The potentiometer transmits an electrical signal determined by measuring flap position to inform the ECU of engine load. See Fig. 3 . In addition to monitoring the air flow, the meter also controls fuel pump operation and idling. At idle, the measuring flap is almost closed due to spiral spring pressure.
An idle air by-pass receives air from main air flow through a small hole, the size of which is controlled by the idle mixture screw. This adjustable air by-pass influences CO levels at low engine speeds.